1. Field of the Invention
The present invention relates to a multi-beam scanner for scanning laser beams emitted from a plurality of laser light sources at fixed time intervals in a prescribed direction. The present invention also relates to an image-forming device equipped with this multi-beam scanner.
2. Description of Related Art
Image-forming devices such as laser p-inters, photocopiers, and facsimile machines have been provided with laser scanners for irradiating a laser beam onto a photosensitive drum in order to form images thereon. Such a laser scanner is provided with a laser diode, a polygon mirror for scanning the laser beam in a main scanning direction, and the like.
The laser beam produced by the laser diode is modulated according to image data and irradiated onto the surface of the photosensitive drum beginning from a prescribed image-writing start position. A beam detect (BD) sensor is provided for detecting this image-writing start position. The BD sensor is disposed within the scanning range of the laser beam so as to receive the laser beam at a prescribed position preceding the image-writing start position. The BD sensor outputs a sensor signal corresponding to the amount of received light. As will be described later, a synchronization signal (BD signal) for setting the image-writing start position is outputted based on the sensor signals received from the BD sensor. More specifically, a BD signal is outputted when the amount of light received by the BD sensor reaches or exceeds the required amount of light for forming electrostatic latent images when irradiated on the photosensitive drum.